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... i doesn't know anybody, or doesn't trust anybody, he will choose to trust the pre-trusted peers. Malicious Collectives. In peer-to-peer networks, there is potential for malicious collectives to form =-=[8]-=-. A malicious collective is a group of malicious peers who know each other, who give each other high local trust values and give all other peers low local trust values in an attempt to subvert the sys...

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...cally with other sensors, and send their sensor readings to the base station. The deployment methods of sensors varies from individual installation of each sensor node, to aerial scattering from an airplane or rocket. Achieving secure communication in sensor networks is a challenging problem for many reasons. Wireless communication is a medium that is difficult to secure against such attacks as eavesdropping and packet injection. Due to the lack of physical interfaces, attackers find it easier to claim multiple identities to the network; this attack is described by Douceur as the Sybil attack [10]. 1 The limited computation and power resources of sensor nodes also often makes it undesirable to use publickey algorithms, such as Diffie-Hellman key agreement [9] or RSA [20]. Currently, a sensor node may require on the order of tens of seconds up to minutes to perform these operations [8, 7]. Even with possible future advances in low-power cryptographic hardware, the performance gap between asymmetric and symmetric cryptosystems is several orders of magnitude and unlikely to be closed soon. In designing security systems for sensor networks, therefore, it is highly desirable to use only fas...

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...em. For example, a file sharing user might want to locate and retrieve a close-by replica of a file, while avoiding server or network failures. Security is also an important concern. The Sybil attack =-=[35]-=- is an attack where a user obtains a large number of identities to mount collusion attacks. Tapestry addresses this by using a trusted public-key infrastructure (PKI) for nodeID assignment. To limit d...

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... when attackers cannot choose nodeIds, they may still be able to mount all the attacks above (and more) if they can obtain a large number of legitimate nodeIds easily. This is known as a Sybil attack =-=[10]-=-. Previous approaches to nodeId assignment have either assumed nodeIds are chosen randomly by the new node [5] or compute nodeIds by hashing the IP address of the node [20]. Neither approach is secure...

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...tablish a pairwise key with any other nodes that have also erased KI (but a newly added node can still establish a pairwise key with it anyway). This helps prevent node clone attacks or sybil attacks =-=[8]-=-. In a clone attack, an attacker loads its own nodes with the keys of a compromised node, then deploys these cloned nodes in different locations of the sensor network. These cloned nodes then try to e...

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...uns multiple instances of Tarzan on different IP addresses. There are no known techniques to prevent this type of attack in a large-scale distributed system without some trusted centralized authority =-=[8, 9]-=-. 34However, Tarzan provides practical measures to lessen the impact of such attacks. First, nodes distribute their keys indirectly through a gossiping protocol. Second, tunnel initiators choose mimi...

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...ese messages are not susceptible to traffic analysis or denial-ofservice attacks by machines located outside of the administrative domain. Indeed, SkipNet even provides resiliency to the Sybil attack =-=[9]-=-: creating an unbounded number of nodes outside microsoft.com will not allow the attacker to see any traffic internal to microsoft.com. An attacker might attempt to target a particular domain (for exa...